In piece commodities, such as pickles containing seasoning liquids or candies, the seasoning liquids or the commodities themselves tend to fall out of the packaging bags. As an approach to this problem, U.S. Pat. No. 4,580,393 or U.S. patent application No. 06/919,649 discloses an apparatus for vacuum packaging a material by feeding a soft packaging bag, in its flat form, to a clamper which is rotated integrally with a vacuum chamber by a rotor, clamping the bag in a suspended state by the clamper, opening said packaging bag to put a material therein, feeding said packaging bag to a vacuum chamber, where said material is vacuum-packaged.
In said apparatus, a number of clampers are moved along a circular path and successively stopped at a bag feeding position, while in said bag feeding position packaging bags are pneumatically attracted one by one, by a vacuum cup, from the top of a stack of packaging bags and transferred to the clampers. However, during the time such operation is repeatedly effected in harmony with the movement of the clampers, there occur such errors as the vacuum cup failing to attract a packaging bag owing to a distortion in the bag, a packaging bag falling from the vacuum cup owing to air resistance when it is transferred by the vacuum cup to a clampers, and the clamper failing to clamp the packaging bag correctly. Besides these, there also occurs an error when the packaging bag is opened, resulting in a material to be packaged being discharged outside the packaging bag during filling operation. Thus, such apparatus has a drawback that such errors, occurring at a rate of 2-3%, cannot entirely be eliminated.